Stage structure in bonding machine and method for controlling the same

ABSTRACT

Stage structure in a bonding machine including a plate movably fitted in a bonding chamber, a plurality of blocks of electro-static chucks fitted to the plate for providing an electro-static force to hold a substrate, a plurality of vacuum holes in the plate around the electro-static chucks for receiving a vacuum force, and adsorbing and holding the substrate, and a plurality of alignment mark confirming holes in a periphery of the plate for confirming the marks for aligning the adsorbed substrate, thereby separating substrate from the stage more easily by applying a DC power with polarities opposite to a regular DC power.

This application claims the benefit of the Korean Application Nos.P2002-0014998 and P2002-0015077, both filed on Mar. 20, 2002, which arehereby incorporated by reference for all purposes as if fully set forthherein.

This application incorporates by reference two co-pending applications,Ser. No. 10/184,096, filed on Jun. 28, 2002, entitled “SYSTEM AND METHODFOR MANUFACTURING LIQUID CRYSTAL DISPLAY DEVICES” (Attorney DocketNumber 8733.666.00) and Ser. No. 10/184,088, filed on Jun. 28, 2002,entitled “SYSTEM FOR FABRICATING LIQUID CRYSTAL DISPLAY AND METHOD OFFABRICATING LIQUID CRYSTAL DISPLAY USING THE SAME” (8733.684), as iffully set forth herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a bonding machine for fabrication of aliquid crystal display, and, more particularly, to a stage structure ina bonding machine for fabricating a liquid crystal display (LCD) havingthe liquid crystal dropping method applied thereto, and a method forcontrolling a bonding machine.

2. Background of the Related Art

Keeping pace with development of an information oriented society,demands on displays increase gradually in a variety of forms, and,recently to meet the demands, different flat display panels, such asLiquid Crystal Display (LCD), Plasma Display Panel (PDP), ElectroLuminescent Display (ELD), Vacuum Fluorescent Display (VFD), and thelike, have been under development, and some of which are employed asdisplays in various apparatuses.

The LCDs have been used most widely as mobile displays while the LCDreplaces the Cathode Ray Tube (CRT) owing to features and advantages ofexcellent picture quality, lightweight, thin, and low power consumption.Besides the mobile type LCDs, such as a notebook computer monitors, LCDsare under development for television (TVs) for receiving and displayingbroadcasting signals, and monitors of computers.

Despite the various technical developments in the LCD for serving as adisplay in different fields, the efforts for enhancing a picture qualityof the LCD as a display are inconsistent with the features andadvantages of the LCD in many aspects. Therefore, for the LCD beingemployed in various fields as a general display, a key for developmentof the LCD lies in how much the LCD is made to implement a high qualitypicture, such as high definition and high luminance, and a large sizedscreen while the LCD is maintained to have the features of light weight,thin, and low power consumption.

The LCD may be fabricated by a generally known LCD injection method, inwhich one substrate having sealant coated thereon so as to form aninjection hole is bonded to the other substrate under a vacuum, andliquid crystal is injected therein through the injection hole in thesealant, or by a liquid crystal dropping method. The liquid crystaldropping method is disclosed in Japanese Patent Laid Open PublicationNos. 2000-284295, and 2001-005405, in which one substrate having liquidcrystal dropped thereon and the other substrate are provided, and thetwo substrates, placed oppositely in a vertical direction, are broughtcloser to bond the two substrates.

Of the two methods, the liquid crystal dropping method is advantageousin that many steps (such as the step of formation of the liquid crystalinjection hole, the step of injection of liquid crystal, and the step ofsealing the liquid crystal injection hole) can be omitted, and lessequipment is required. Accordingly, studies for development of variousapparatuses for use in the liquid crystal dropping method have beenmade.

FIGS. 1 and 2 illustrate a related art bonding machine having the liquidcrystal dropping method applied thereto.

The related art bonding machine is provided with a frame 10 forming anouter shape, stage parts 21 and 22, a sealant outlet part (not shown), aliquid crystal dropping part 30, chamber parts 31 and 32, chamber movingmeans, and stage moving means.

The stage parts have an upper stage 21 and a lower stage 22, and thereis an electro-static chuck 28 at a bottom the upper stage 21. Theelectro-static chuck 28, which is an insulating material plate havingtwo rectangular recesses, each with a plate electrode built thereincovered with a dielectric material of which main surface is on the sameplane with a bottom surface of the electro-static chuck 28. Each of theburied plate electrodes (not shown) is connected to a positive/negativeDC power through an appropriate switch. When a positive or a negativevoltage is applied to the plate electrodes, a negative or positivecharge is induced at the main surface of the dielectric material on thesame plane with the bottom surface of the electro-static chuck 28, toadsorb the substrate by a Coulomb force generated between the substrate51 and the transparent electrode film caused by the charge.

The sealant outlet part and the liquid crystal dropping part 30 isfitted to a side of a location at which the frame is bonded, and thechamber-part has an upper chamber unit 31 and a lower chamber unit 32,detachable from each other.

The chamber moving means has a driving motor 40 for selective movementof the lower chamber unit 32 to a location the bonding is made, or to alocation discharge of the sealant and dropping of the liquid crystal ismade, and the stage moving means has a driving motor 50 for driving theupper stage 21 upward or downward, selectively.

The steps of a method for fabricating an LCD by using the foregoingrelated art bonding machine will be explained in detail.

First, the second substrate 52 is loaded on the lower stage 22 in thelower chamber unit, -and the lower chamber unit 32 is moved toward alocation the upper stage 21 is located by driving the driving motor 40of the chamber moving means.

Under this state, the upper stage 21 produces a vacuum adsorbing force,and adsorbs the second substrate 52 by vacuum, and the lower chamberunit 32 is moved to a location for coating sealant and dropping liquidcrystal by driving the driving motor 40.

Then, the first substrate 51 is brought into the lower stage 22, and,then, the lower stage 22 produces a vacuum adsorption force, and vacuumadsorbs the first substrate 51. This state is illustrated in FIG. 1.

Under this state, the lower chamber unit 32 having the lower stage 22 ismoved to a location for coating sealant and dropping the liquid crystalby the chamber moving means 40.

Then, when the sealant coating and the liquid crystal dropping arefinished by the sealant outlet part and the liquid crystal dropping part30, the lower chamber unit 32 is moved to a location for bonding thesubstrates by the chamber moving means 40, again, as shown in FIG. 2.

Then, chamber units 31 and 32 are bonded by the chamber moving means 40,to close the spaces where the respective stages 21 and 22 are locatedrespectively, and the spaces are evacuated by separate vacuum means. Inthis instance, the second substrate 52 vacuum adsorbed at the upperstage falls down onto a catch stop pawl (not shown), and theelectro-static chuck 28, having a voltage applied thereto at a time thechamber is evacuated adequately, adsorbs the second substrate 52 on thecatch stop pawl.

Then, the upper stage 21 is moved downward such that the secondsubstrate 52 adsorbed at the upper stage 21 is brought into contactwith, and pressed down to, the first substrate 51 adsorbed at the lowerstage 22, to bond the substrates, thereby finishing fabrication of theLCD.

However, the foregoing related art assembler (bonding machine) has thefollowing problems.

First, because the related art bonding machine has a system in which thesealant coating and the liquid crystal dropping are made on thesubstrate having the thin film transistors formed thereon, and thesubstrate having the color filter layer formed thereon, the related artbonding machine becomes bulky by the parts for carrying out the sealantcoating and the liquid crystal dropping.

Particularly, the bonding machine for large sized LCDs required recentlybecomes more bulky, such that fabrication of the large sized LCDs isunfavorable.

Second, if the sealing in the coupling between the lower chamber unitand the upper chamber unit is not perfect, the substrates may be damagedduring the bonding, and the bonding may be defective due to infiltrationof air through a leakage part. Accordingly, parts for prevention of airleakage is additionally required in the vacuum state, and the requiredaccuracy causes difficulty.

Third, the electro-static chuck of two plate electrodes, absorbing thesubstrate by having voltages of different poles applied thereto, arelikely to drop the substrate as the electro-static absorbing force isnot adequate. Moreover, the large sized glass substrate cannot beadsorbed.

Fourth, the alignment of the substrates by moving the lower chamber unitin a lateral direction in bonding the substrates is very difficult,which increases a time period required for the entire fabrication. Thatis, because there are many movements required for the fabrication, suchas the movement of the lower chamber unit to a location for dropping theliquid crystal or coating the sealant onto a substrate held at the lowerstage, and the returning of the lower chamber to a location for bondingthe substrates again when above process is finished, accuracy of thesubstrate alignment cannot be secured.

Fifth, as explained, even if the power to the electro-static chuck 28 iscut off for separating the substrates from the upper/lower stages afterthe bonding is finished, the potential remaining between the upper stageand the bonded substrates may impede easy separation of the bondedsubstrates, which causes misalignment of the bonded substrates, anddeterioration of adhesive force of the sealant.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a stage structure in abonding machine for fabricating a liquid crystal display, and a methodfor controlling a bonding machine that substantially obviates one ormore of the problems due to limitations and disadvantages of the relatedart.

An advantage of the present invention is to provide a stage structure ina bonding machine for fabricating a liquid crystal display (LCD), whichcan provide a bonding machine which has a size optimized to an overalllayout, movement ranges, and directions of stages simplified for smoothalignment of the substrates. The time period required for fabrication ofone LCD is shortened for smooth process design in relation to otherprocesses, and which can separate the substrates from the stage moresmoothly in releasing the electro-static adsorption after theelectro-static adsorption, and a method for fabricating a bondingmachine is provided.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, the stagestructure in a bonding machine includes a plate movably fitted in abonding chamber; a plurality of blocks of electro-static chucks fittedto the plate for providing an electro-static force hold a substrate; aplurality of vacuum holes in the plate around the electro-static chucksfor receiving a vacuum force and adsorbing and holding the substrate;and a plurality of alignment mark confirming holes in a periphery of theplate confirming of the marks for aligning the adsorbed substrate.

The block of electro-static chucks includes a plurality of plateelectrode pairs for having voltages of opposite polarities appliedthereto.

The plate electrode has a voltage of a polarity opposite to polaritiesof adjacent plate electrodes applied thereto.

The electro-static chucks in each of the blocks have different sizes.

The plurality of alignment mark confirming holes includes at least tworough mark holes and at least four fine mark holes.

The stage structure in a bonding machine further includes lift bar holesin the plate for supporting the substrate during loading the substrate,or lifting the substrate from the stage during unloading.

The electro-static chucks include six blocks.

The one block of electro-static chucks includes four plate electrodes.

The plate electrode has a voltage of a polarity opposite to polaritiesof adjacent plate electrodes applied thereto.

The stage structure in a bonding machine further includes at least oneor more than one spare holes in a central part of the plate.

The plurality of alignment mark confirming holes include at least onehole in a cut away part of a corner of the electro-static chuck in eachof corners of the upper stage.

The stage structure in a bonding machine further includes a plurality offixing holes in a periphery of the plate for fixing the bondedsubstrates.

In another aspect of the present invention, there is provided a stagestructure in a bonding machine having an upper stage and a lower stageincluding a plurality of blocks of first electro-static chucks fitted tothe upper stage for providing an electro-static force to hold asubstrate; a plurality of first vacuum holes in the upper stage aroundthe electro-static chucks for receiving a vacuum force to adsorb andhold the substrate; a plurality of first alignment mark confirming holesin a periphery of the upper stage for confirming marks for aligning theadsorbed substrate; a plurality of blocks of second electro-staticchucks fitted to the lower stage for providing an electro-static forceto hold the substrate; and a plurality of second vacuum holes in thelower stage around the electro-static chucks for receiving a vacuumforce to adsorb and hold the substrate.

The stage structure in a bonding machine further includes a plurality offirst fixing holes in a periphery of the upper stage for fixing thebonded substrates, and a plurality of second fixing holes in a peripheryof the lower stage for fixing the bonded substrates.

The plurality of first fixing holes and the plurality of second fixingholes are formed at locations different from each other.

The stage structure in a bonding machine further includes lift bar holesin the lower stage for supporting the substrate during loading thesubstrate, or lifting the substrate from the stage during unloading.

The stage structure in a bonding machine further includes a plurality ofsecond alignment mark confirming holes in a periphery of the lower stagefor confirming marks for aligning the adsorbed substrate.

The plurality of first or second alignment mark confirming holes includeat least two rough mark holes and at least four fine mark holes.

The second alignment mark confirming hole has a light providedtherethrough.

The electro-static chucks include six blocks, and each block includesfour plate electrodes.

In further aspect of the present invention, there is provided a methodfor controlling a bonding machine having upper and lower stages eachwith electro-static chucks, each chuck having a plurality of plateelectrodes, the method including: applying voltages of either negativeor positive polarity to the plate electrodes in the electro-staticchuck, and the upper and lower stages adsorbing respective substrates byusing the electro-static chucks; moving the upper and the lower stages,to bond the substrates, and cutting off the voltages applied to theelectro-static chucks; applying voltages of opposite polarities to theplate electrodes respectively, and moving the upper or lower stage.

In still a further aspect of the present invention, there is provided amethod for controlling a bonding machine having upper and lower stages,each with electro-static chucks, each chuck having a plurality of plateelectrodes, the method including: loading a first substrate and a secondsubstrate in the bonding chamber; evacuating the bonding chamber;applying voltages of either negative or positive polarity to the plateelectrodes in the electro-static chuck, and the upper and lower stagesadsorbing respective substrates by using the electro-static chucks;moving the upper and the lower stages, to bond the substrates, andcutting off the voltages applied to the electro-static chucks; andapplying voltages of opposite polarities to the plate electrodesrespectively, and moving the upper or lower stage.

The method for controlling a bonding machine further includes aligningthe substrates adsorbed at the upper and lower stages after applyingvoltages of either negative or positive polarity to the plateelectrodes.

The method for controlling a bonding machine further includes ventingthe bonding chamber for applying pressure to the bonded two substrates,and unloading the pressed first, and second substrates, after the stepof cutting off the voltages applied to the electro-static chucks;applying voltages of opposite polarities to the plate electrodesrespectively, and moving the upper or lower stage.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention:

In the drawings:

FIG. 1 illustrates a substrate bonding machine having a related artliquid crystal dropping method applied thereto in dropping the liquidcrystal;

FIG. 2 illustrates a substrate bonding machine having a related artliquid crystal dropping method applied thereto in bonding thesubstrates;

FIG. 3 illustrates a bonding machine for fabricating an LCD having aliquid crystal dropping method applied thereto in accordance with anembodiment of the present invention, schematically;

FIG. 4 illustrates a plan view of an electro-static chuck in a bondingmachine in accordance with an embodiment of the present invention,schematically;

FIG. 5 illustrates a section across a line I-I′ in FIG. 4;

FIG. 6 illustrates a detailed plan view of an upper stage in a bondingmachine in accordance with an embodiment of the present invention; and

FIG. 7 illustrates a detailed plan view of a lower stage in a bondingmachine in accordance with an embodiment of the present invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to embodiments of the presentinvention, examples of which are illustrated in the accompanyingdrawings.

FIG. 3 illustrates a bonding machine for fabricating a liquid crystaldevice (LCD) having a liquid crystal dropping method applied thereto inaccordance with an embodiment of the present invention, schematically.

It is suggested that the bonding machine of the present inventionincludes a bonding chamber 110, a stage part, a stage moving device(unlabeled), an evacuation device (unlabeled), a vent device(unlabeled), and a loader part 300.

The bonding chamber 110 includes an inside space for carrying outbonding by pressing the substrates to each other, and bonding by using apressure difference in succession by selectively making the space avacuum state, or an atmospheric state, and an opening 111 in one sidefor moving the substrate in or out.

The bonding chamber 110 further includes an air extraction tube 112connected to one side thereof for extracting air from the inside spaceof the bonding chamber 110 by an air suction power from the evacuationdevice, and a vent tube 113 connected to the one side thereof forintroducing external air or other gas N₂ into the bonding chamber 110,for placing the bonding chamber 110 in the vacuum state, or in theatmospheric state, selectively.

The air extraction tube 112 and the vent tube 113 have electronicallycontrolled valves 112 a and 113 a respectively, for selectivelyopening/shutting of tube lines.

Together with this, it is suggested to provide a door (not shown) to theopening 111 in the bonding chamber 110 for selectively closing theopening.

The door 111 a may be a general sliding, or rotating type door, or otherdevice that can close an opening, and the sliding, or rotating type doorhas a sealing member for sealing a gap, of which detail is not shown inthe drawing.

The stage part includes an upper stage 121 and a lower stage 122 fittedin an upper space and a lower space respectively, in the bonding chamber110 to face each other, for holding the substrates 510 and 520 broughtinto the bonding chamber 110 by the loader part 300 at requiredprocessing positions.

It is suggested that the upper stage 121 has at least one Electro StaticChuck (ESC) 121 a fitted to a recess in a bottom of the upper stage 121for holding the substrate by electro static force, and at least onevacuum hole 121 b for adsorbing and holding the substrate by vacuum.

Though the present-embodiment suggests at least two ESCs 121 a to formpairs each having DC voltages of opposite polarities applied thereto forelectro static holding of the substrate, the present invention is notlimited to this, but may be designed such that one ESC has the DCvoltages of opposite polarities applied thereto for providing theelectro static power.

The upper stage 121 has a plurality of vacuum holes 121 b formed aroundeach of the ESCs 121 a fitted to the bottom of the upper stage 121 andconnected to single or multiple tube lines 121 c for communication witha vacuum pump 123 connected to the upper stage 121.

Together with this, it is suggested that the lower stage 122 has atleast one ESC 122 a on a top surface of the lower stage for providingelectro static power to hold the substrate, and at least one vacuum hole(not shown) for adsorbing and holding the substrate by vacuum.

The ESC and the vacuum hole may, or may not be identical to the same ofthe upper stage 121, but arrangements of electro static power providingdevices and the vacuum holes are made taking an overall fabricationprocess of the substrates or each liquid crystal coating region intoaccount.

The stage moving device includes a moving shaft 131 for selectivelymoving the upper stage 121 up/down, a rotating shaft 131 for selectiveleft/right rotation of the lower stage 122, and driving motors 133 and134 fitted to inside or outside of the chamber 110 coupled to the stages121 and 122 via shafts, respectively.

The unexplained symbol 135 denotes driving means driven for lateralmovement of the lower stage 122 in alignment of the substrates.

The bonding machine of the present invention is provided with a suctionpump for transmitting a suction force so that the inside space of thebonding chamber 110 achieves a vacuum state selectively, and for beingdriven to produce a general air suction force. A space the suction pump200 is provided with is formed such that the space is in communicationwith the air extraction tube 112 of the bonding chamber 110.

The loader part, a device separate from the bonding chamber 110 and thevarious components in the bonding chamber 110, is fitted to an outsideof the bonding chamber 110, for receiving and selectively carrying thefirst substrate 510 having the liquid crystal dropped thereon, or thesecond substrate 520 having the sealant coated thereon, into or out of,the bonding chamber 110.

The loader part includes a first arm 310 for carrying the firstsubstrate 510 having the liquid crystal dropped thereon, and a secondarm 320 for carrying the second substrate 520 having the sealant coatedthereon, wherein it is designed that the first arm 310 is positionedabove the second arm 320 in a standby state before the first and secondsubstrates 510 and 520, loaded on relevant arms 310 and 320, are carriedinto the inside space of the bonding chamber 110.

Moreover, it is additionally suggested that the bonding machine of thepresent invention further includes an alignment device 600 forconfirming an alignment state between the substrates 510 and 520 carriedinto the bonding chamber 110 by the loader part and loaded on the stages121 and 122 respectively, when, although the alignment device 600 may befitted to at least one of an outside or an inside of the bonding chamber110, the present invention suggests that the alignment device 600 isfitted to the outside of the bonding chamber 110, as one embodiment.

Thus, the foregoing bonding machine in accordance with an embodiment ofthe present invention is made to have an overall size significantlyreduced in comparison to the related art bonding machine by making theformation of the substrates to be done in other processes separately,and can shorten a fabrication time period significantly by making thebonding machine to carry out a simple bonding process only.

Moreover, the foregoing system of the present invention permits fasterand more accurate alignment of the substrates by permitting the lowerstage to move within an extremely limited range only. Different from therelated art, since the foregoing system of the present invention doesnot have a two pieced chamber to couple/decouple selectively, but a onepieced chamber, the foregoing system of the present invention caneliminate leakage problems caused when two chambers are coupled, and candispense with many components required for the prevention of theleakage.

The upper stage and the lower stage will be explained in detail. FIG. 4illustrates a plan view of an electro-static chuck in a bonding machinein accordance with an embodiment of the present invention schematically.FIG. 5 illustrates a section across a line I-I′ in FIG. 4.

Referring to FIG. 4, there are a plurality of blocks (6 blocks) ofelectro-static chuck 121 a arranged on a surface of the upper or lowerstage 121 or 122 for providing an electro-static force and adsorbing thesubstrate, wherein each block of the electro-static chuck 121 a includesat least one pair of plate electrodes 1 for applying DC currents ofopposite polarities (negative/positive) thereto, respectively. There isa plurality of vacuum holes 121 b in the upper stage 121 around theelectro-static chucks 121 a, for receiving the vacuum force to adsorband hold the substrate.

Therefore, when either a positive, or negative voltage is applied to theplate electrodes 1, to induce either a negative or positive charge atthe upper/lower stages 121 and 122, the substrate is adsorbed by aCoulomb force generated between a conductive layer such as indium tinoxide (ITO) used for transparent electrodes, such as a common electrode,or pixel electrodes, are formed on the glass substrate 520, and theupper stage by the charges.

The upper stage and the lower stage having the electro-static chucks andthe other elements formed thereon will be explained in detail. FIG. 6illustrates a detailed plan view of an upper stage in a bonding machinein accordance with an embodiment of the present invention. FIG. 7illustrates a detailed plan view of a lower stage in a bonding machinein accordance with an embodiment of the present invention.

Referring to FIG. 6, there are a plurality of blocks (6 blocks) ofelectro-static chucks 121 a each fitted in a recess in a flat surface ofthe upper stage 121 for providing an electro-static force to adsorb thesubstrate, wherein each of the blocks of electro-static chucks 121 aincludes a plurality of pairs of plate electrodes 1 (four plateelectrodes), for applying DC currents of opposite polarities to theplate electrodes 1 in each of the pairs, respectively. The blocks ofelectro-static chucks 121 a have forms different from one another, andfastened with fastening means to the upper stage 121, for an example,with fastening bolts 2.

The electrostatic chuck 121 a may include at least one block havingfour, or more than four plate electrodes 1, and formed opposite to cellregions (active regions) of the substrate.

There are a plurality of vacuum holes 121 b in the upper stage 121around the electrostatic chucks 121 a, for receiving the vacuum force toadsorb and hold the substrate.

There are holes 3 b, 3 d, 3 f, 3 g, 3 i, and 3 k for confirming roughalignment marks and holes 3 a, 3 c, 3 e, 3 h, 3 j, and 3 l forconfirming fine align marks, in the upper stage 121 around theelectrostatic chuck 121 a opposite to the alignment device 600, andthere are corner parts of the plate electrodes 1 cut in ‘L’ forms atcorner parts of the upper stage having holes 3 m, and 3 n formed thereinfor confirming the rough or fine alignment marks. That is, there areholes 3 a-3 l in corner parts (four parts) of the upper stage, and upperand lower side parts of the upper stage formed in pairs, for confirmingthe rough alignment marks and the fine align marks, and there are holes3 a-3 l in corner parts of the plate electrodes 1 formed in pairs, forconfirming the rough alignment marks and the fine alignment marks.Though a general substrate has the rough and fine alignment marks formedat corners of the substrate, there are as many holes for confirming thealignment marks of different sizes of substrates as there are differentsizes of substrates.

Therefore, when the substrate is the largest one, alignment marksthereon are confirmed by using the four pairs of holes 3 a, and 3 b, and3 k, and 3 l, in corner parts of the upper stage, and when the substrateis smaller than the largest one, the alignment marks are confirmed byusing rest of the holes. That is, when the substrate is the largest, aminimum of two rough alignment mark holes in the corner parts areadequate, and more than four rough alignment mark holes are required forcoping with different models, or sizes, if needed, and a minimum of fourfine alignment mark holes are adequate, and more than six fine alignmentmark holes are required for coping with different models, or sizes, ifneeded.

Moreover, the plurality of alignment mark confirming holes is formed insymmetry with respect to a central part.

Though in the explanation of the process for bonding the substrates byusing the bonding machine it is not discussed, there is a highpossibility of misalignment of the bonded substrates caused bydistortion of the bonded substrates coming from pressure change andintroduction of dry air or gas in venting of the bonding chamber foruniform application of pressure to the two substrates after the upperstage 121 is moved down and applies pressure to the substrates adsorbedat the upper stage and the lower stage. Therefore, a process for fixingthe two bonded substrates is carried out before the venting. In thefixing process, light is used for setting the sealant partially, or heator pressure is applied for setting the bonded two substrates. Thus, inorder to fix the bonded two substrates, it is required to direct light,or apply heat to the sealant, additionally.

Accordingly, there are holes 4 a, 4 b, 4 c, 4 d, 4 e, and 4 f in anouter periphery of the electro-static chuck 121 a of the upper stage121, for directing an ultraviolet (LTV) light or partly applying heat tothe sealant. That is, the holes are formed at locations corresponding tolocations of the sealant (fixing sealant) formed between the twosubstrates. Though there are six fixing holes shown in the drawing, anumber of the fixing holes equal to four or more than four are adequate.

Though not shown, there may be spare holes at locations other than theouter periphery of the upper stage, and there are recesses 7 in theouter periphery of the upper stage 121 in parts where a clamp is usedfor entry.

Referring to FIG. 7, similarly, there are also a plurality of blocks (6blocks) of electro-static chucks 122 a each fitted in a recess in thelower stage 122 (plate) for providing an electro-static force to adsorbthe substrate, wherein each of the blocks of electro-static chucks 122 aincludes a plurality of pairs of plate electrodes 1 (four plateelectrodes), for applying DC currents of opposite polarities to theplate electrodes 1 in each of the pairs, respectively. The blocks ofelectro-static chucks 122 a have forms different from one another, andfastened with fastening means to the lower stage 122, for example, withfastening bolts 2.

In the lower stage 122 the electro-static chuck 122 a may also includeat least one block having four or more than four plate electrodes 1, andformed opposite to cell regions (active regions) of the substrate.

However, the polarities of the DC currents applied to the electrostaticchucks of plate electrodes 1 in the upper stage and the lower stage areopposite to each other (Compare FIGS. 6 and 7).

There are a plurality of vacuum holes 122 b in the lower stage 121around the electro-static chucks 122 a, for receiving the vacuum forceto adsorb and hold the substrate.

Similar to the upper stage, there are holes 3 b, 3 d, 3 f, 3 g, 3 i, and3 k for confirming rough alignment marks and holes 3 a, 3 c, 3 e, 3 h, 3j, and 3 l for confirming fine alignment marks in the upper stage 121around the electro-static chuck 121 a opposite to the alignment device600, and there are corner parts of the plate electrodes 1 cut in ‘L’forms at corner parts of the upper stage having holes 3 m and 3 n formedtherein for confirming the rough or fine alignment marks. That is, thereare holes 3 a-3 l in corner parts (four parts) of the upper stage andupper and lower side parts of the upper stage formed in pairs forconfirming the rough alignment marks and the fine alignment marks, andthere are holes 3 a-3 l in corner parts of the plate electrodes 1 formedin pairs, for confirming the rough alignment marks and the finealignment marks. Though a general substrate has the rough and finealignment marks formed at corners of the substrate, there are as manyholes for confirming the alignment marks of different sizes ofsubstrates as there are different sizes of substrates.

Therefore, when the substrate is the largest one, alignment marksthereon are confirmed by using the four pairs of holes 3 a, and 3 b, and3 k, and 3 l, in corner parts of the upper stage, and when the substrateis smaller than the largest one, the alignment marks are confirmed byusing rest of the holes. That is, when the substrate is the largest, aminimum two rough alignment mark holes in the corner parts are adequate,and more than four rough alignment mark holes are required for copingwith different models, or sizes, if needed, and a minimum of four finealignment mark holes are adequate, and more than six fine alignment markholes are required for coping with different models or sizes, if needed.

Moreover, there are holes 4 a, 4 b, 4 c, 4 d, 4 e, 4 f, 4 g, and 4 h inan outer periphery of the electro-static chuck 122 a of the lower stage122, for directing an ultraviolet (UV) light or partly applying heat tothe sealant, to fix the substrate. The fixing holes 4 a-4 h in the lowerstage is formed at locations, which are not the same as the locations ofthe fixing holes 4 a-4 f in the upper substrate, but other parts.Therefore, the sealant sets at locations of the fixing holes 4 a-4 f inthe upper stage and the fixing holes 4 a-4 h in the lower stage. Thoughthere are seven fixing holes shown in FIG. 7, a number of the fixingholes equal to four or more than four are adequate.

There are holes 5 in the lower stage for supporting the substrate, orlifting the substrate from a surface of the lower stage when thesubstrate is loaded on, or unloaded from the lower stage, and there maybe spare holes 6 a, 6 b, 6 c, 6 d, 6 e, and 6 f.

If a camera is fitted in an upper stage side for confirming the roughalignment marks and the fine alignment marks, a light is provided from alower stage side through the mark alignment confirming holes in thelower stage, and opposite to this, if the camera is fitted in a lowerstage side, the light is provided through the mark alignment confirmingholes in the upper stage, for serving as a back light of the camera.

The rough mark confirming holes, the fine mark confirming holes, andfixing holes in each of the stages may be formed as required accordingto dummy regions of the substrate held at the stages.

A process for bonding the substrates by using the foregoing bondingmachine for an LCD of the present invention, and a method for driving anelectro-static chuck of the stages will be explained.

At first, a first substrate having liquid crystal dropped thereon, and asecond substrate having sealant coated thereon, are provided. Of course,the first substrate may have both the liquid crystal dropped thereon,and the sealant coated thereon.

As shown in dashed lines in FIG. 3, the loader part 300 puts the firstsubstrate 510 having the liquid crystal dropped thereon on standby on anupper side by using a first arm 310, and receives and puts the secondsubstrate 520 having the sealant coated thereon under the first arm 310by using the second arm 320.

In this state, when the opening 111 in the bonding chamber 110 isopened, the loader part controls the second arm 320, so that the secondarm 320 loads the second substrate 520 having the sealant coated thereoninto the bonding chamber 110 through the opened opening. The upper stage121 is moved downward to an upper side of the second substrate 520, andthe vacuum pump 123 connected to the upper stage 121 is put intooperation, to adsorb the second substrate 520 carried in by the secondarm 320 by the vacuum transmitted to the vacuum holes 121 b in the upperstage 121. Then, the upper stage 121 is moved upward, to load the secondsubstrate.

Then, the loader part controls the first arm 310, to load the firstsubstrate 510 having the liquid crystal dropped thereon into the bondingchamber 110, and place on the lower stage 122, makes the lower stage 122to adsorb the first substrate 510 carried in by the first arm 310 by avacuum from the vacuum holes (not shown) in the lower stage 122 as thevacuum pump (not shown) connected to the lower stage 122 is put intooperation, to hold the first substrate 510 at the lower stage 122.

The second substrate 520 having the sealant coated thereon is carried inbefore the first substrate 510 having the liquid crystal droppedthereon, for prevention of dust and the like, that can be producedduring the carrying in of the second substrate 520, from falling downonto the liquid crystal dropped on the first substrate 510, when thefirst substrate 510 is carried in before the second substrate 520.

If substrates are bonded on the lower stage from a prior bondingprocess, loading and unloading are carried out simultaneously forshortening the fabrication time period by making the second arm 320unload the bonded substrates on the lower stage after the second arm 320carries in the second substrate.

Upon finishing loading of the substrates 510 and 520 by the foregoingsteps, the arms 310 and 320 in the loader part 300 move out of thebonding chamber 110, and the door to the substrate opening 111 in thebonding chamber 110 is put into operation, to close the substrateopening 111, to leave the bonding chamber 110 in a closed state.

Then, though not shown in the drawings, the substrate receiver isbrought to a location under the upper stage, the second substrateadsorbed to the upper stage is placed down on the substrate receiver,and evacuation of the chamber is started.

That is, by putting the suction pump (evacuation device) 200 in theevacuation device into operation to generate an air suction force, andmaking the valve 112 a on the air extraction tube 112 to the bondingchamber 110 leave the air extraction tube in an opened state, totransmit the air suction force generated from the suction pump 200 to aninside of the bonding chamber 110, the inside of the bonding chamber 110can be placed in a vacuum state.

Thus, when the suction pump 200 is driven for a time period to obtain arequired vacuum in the bonding chamber 110, the suction pump 200 isstopped, and the air extraction tube 112 is closed by operating thevalve 112 a.

When the bonding chamber 110 is evacuated fully, power is provided tothe ESC 121 a and 122 a so that the upper-stage 121 and the lower stage122 adsorb respective substrates 510 and 520, electrostatically. Then,the substrate receiver is returned to an original location.

In this instance, approximately 0.1-1 KV is applied when a surface ofthe substrate having a conductive layer formed thereon is positioned ona stage side, and approximately 3-4 KV is applied when a surface of thesubstrate having a conductive layer formed thereon is positioned on aside opposite to the stage.

Under this state, the stage moving device drives the driving motor 133,to move the upper stage 121 down close to the lower stage 122, and,along with this, the alignment device 600 determines an alignment stateof the substrates 510 and 520 held to respective stages 121 and 122, andprovides control signals to the moving shafts 131 and 132 and therotation shafts coupled to respective stages 121 and 122, for aligningthe substrates.

Then, the stage moving device keeps receiving a driving signal, and isdriven continuously, to press the second substrate 520 ESC adsorbed tothe upper stage 121 down to the first substrate 510 adsorbed to thelower stage 122, thereby completing a primary bonding between the twosubstrates. The primary bonding herein does not complete a bondingprocess by moving and pressing the substrates 121 and 122, but thebonding is only to the extent that no air enters between the substrateswhen the pressure is changed to the atmospheric pressure.

Therefore, when the primary bonding process is finished, the power tothe ESC 121 a is cut off, to release the substrate from the upper stage,and the upper stage 121 is moved upward. Then, the valve 113 a isopened, to introduce dry air or N₂ gas into the bonding chamber throughthe vent tube 113, so that a pressure difference is formed inside of thebonding chamber 110 as the inside of the bonding chamber 110 reaches anatmospheric state gradually, that presses the bonded substrates. Since aspace between the first, and second substrates sealed by the sealant isat a vacuum, and the bonding chamber is at the atmospheric pressure, thefirst, and second substrates are pressed, uniformly.

Eventually, an improved bonding of the substrates can be made, and, uponfinishing the bonding, the door 114 to the bonding chamber 110 isdriven, to open the substrate opening 111 closed by the door.

Thereafter, the substrate bonding is performed by carrying out unloadingof the bonded substrates by means of the loading part 300, andrepeatedly carrying out the foregoing series of steps.

In the meantime, as explained, there is possibility that even if thepower to the electro-static chuck 28 is cut off for separating thesubstrates from the upper/lower stages after the bonding is finished,the potential remaining between the upper stage and the bondedsubstrates may impede easy separation of the bonded substrates, whichcauses misalignment of the bonded substrates, and deterioration ofadhesive force of the sealant.

Therefore, in the present invention, voltages of opposite polarities areapplied to the plate electrodes 1 of the ESC momentarily at the time thepower to the ESC 121 a is cut off, for easy separation of the bondedsubstrates from the upper stage.

Voltages of either positive or negative polarity are applied torespective plate electrodes 1, to adsorb the substrates by a Coulombforce generated between the ITO conductive layer on the glass substrate520 and the upper stage, and voltages of polarities opposite to thepolarities of the voltages applied for adsorbing the substrates areapplied to respective plate electrodes 1 simultaneously with cutting offthe power applied to the plate electrodes 1, for easy separation of thebonded substrates from the stage. Then, the charges remaining betweenthe stage and the substrates are offset, which facilitates the easyseparation of the bonded substrates from the stage.

As has been explained, the stage structure in a bonding machine forfabricating an LCD, and the method for controlling a bonding machine ofthe present invention have the following advantages.

First, because the bonding machine of the present invention is separatefrom apparatuses for dropping liquid crystal and coating sealant, toreceive substrates fabricated through other processes, a system requiredfor forming a liquid crystal layer and seals on the substrate loaded onthe lower stage in the related art bonding machine can be dispensedwith, and an overall size of the bonding machine can be reducedsignificantly, thereby permitting an effective lay-out design, andsaving an installation space.

The independent progression of the dropping of liquid crystal, thecoating of sealant, and the bonding of substrates shortens a totalfabrication time period.

Third, the extremely restricted movement of the lower stage in thevacuum chamber of the bonding machine of the present invention permitsfast and precise position alignment of the substrates by lateralmovement of the lower chamber unit similar to the related art.Particularly, different from the related art, the one pieced chamber ofthe present invention, unlike the two pieced vacuum chamber forselective coupling/decoupling, eliminates the problem of leakage whenthe two pieced chamber is coupled, and dispense with many componentsrequired for prevention of the leakage.

Fourth, since the loader part is designed such that the arm that carriesthe substrate having no crystal dropped thereon into the vacuum chambercarries the bonded substrates placed on the lower stage in a bondedstate bonded through prior processes out of the vacuum chamber in aprocess of carrying in the substrate, a working time period for carryingin the substrate and carrying out the bonded substrates can beshortened.

Fifth, the provision of, not only the vacuum adsorption holes in theupper and lower stages, but also the electro-static chucks forelectro-static adsorption permits stable adsorption of the substratesduring evacuation of the bonding chamber, which permits the evacuationand bonding processes to be carried out more smoothly.

Sixth, the mark alignment holes in the stages permit more accuratealignment of the two substrates as the marks in the substrates can beconfirmed by the camera in bonding the two substrates.

Seventh, the fixation of the bonded substrates by using the fixing holesin the stages after bonding the two substrates prevents misalignment ofthe substrates which can occur during venting and improve yield.

Eighth, the easy separation of the bonded substrates from the upperstage by applying voltages of opposite polarities to the plateelectrodes in the electro-static chuck before moving up the upper stageafter the two substrates are adsorbed and bonded by using theelectro-static chuck prevents occurrence of misalignment of thesubstrate and deterioration of adherence of the sealant caused by apotential remaining between the upper stage 121 and the bondedsubstrates when the upper stage 121 is moved upward.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the stage structure in abonding machine for fabricating an LCD, and the method for controlling abonding machine of the present invention without departing from thespirit or scope of the invention. Thus, it is intended that the presentinvention cover the modifications and variations of this inventionprovided they come within the scope of the appended claims and theirequivalents.

1-20. (canceled)
 21. A method for controlling a bonding machine havingupper and lower stages, each with electro-static chucks, each chuckhaving a plurality of plate electrodes, the method comprising: applyingvoltages of one of negative and positive polarity to the plateelectrodes in the electro-static chuck, and the upper and lower stagesadsorbing respective substrates by using the electro-static chucks;moving the upper and the lower stages to bond the substrates; andcutting off the voltages applied to the electro-static chucks, applyingvoltages of opposite polarities to the plate electrodes respectively,and moving one of the upper and lower stages.
 22. A method forcontrolling a bonding machine having upper and lower stages, each withelectro-static chucks, each chuck having a plurality of plateelectrodes, the method comprising: loading a first substrate and asecond substrate in the bonding chamber; evacuating the bonding chamber;applying voltages of one of negative and positive polarity to the plateelectrodes in the electro-static chuck, and the upper and lower stagesadsorbing respective substrates by using the electro-static chucks;moving the upper and the lower stages to bond the substrates; andcutting off the voltages applied to the electro-static chucks, applyingvoltages of opposite polarities to the plate electrodes respectively,and moving one of the upper and lower stages.
 23. A method as claimed inclaim 22, further comprising aligning the substrates adsorbed at theupper and lower stages after applying voltages of one of negative andpositive polarity to the plate electrodes.
 24. A method as claimed inclaim 22, further comprising: venting the bonding chamber for applyingpressure to the bonded two substrates; and unloading the pressed firstand second substrates, after cutting off the voltages applied to theelector-static chucks, applying voltages of opposite polarities to theplate electrodes respectively, and moving one of the upper and lowerstages.